This invention relates to gas turbine engine exhaust nozzles and particularly to a two-dimensional configuration having a movable and collapsible wall centerbody and the sealing, cooling and pressurizing means therefore.
The efficacy which a centerbody operates in the exhaust of the jet engine is dependent not only on its construction but, of equal importance, on the means for cooling and pressure balancing it. One of the major problems in a cooling scheme of an articulate centerbody pivotable, particularly at more than one pivot point, and one that has its walls collapsible, is the sealing in of internal cooling air and sealing out the hot exhaust products of combustion of the engine. It is abundantly important to hold friction at a minimum.
This invention contemplates sealing the centerbody of a two-dimensional nozzle configured to change the nozzle area, provide thrust vectoring and internal nozzle expansion. A wedge shaped segmented centerbody having pivot points to change its orientation, and having collapsible walls to change its distance relationship with the cooperating side wall of the nozzle serves to provide these functions. The centerbody extends to opposite flat side walls of the nozzle and is in sliding relationship thereto; for both the pivoting and collapsing modes. The movement of the centerbody and its wall structure is accomplished by appropriate actuator and linkages mounted within the centerbody.
We have found that we can achieve a satisfactory sealing at the side walls while incurring minimal flow losses and holding friction to a minimum by incorporating spaced elongated seal elements secured to the centerbody defining therewith an open ended channel adapted to channel pressurized cooling air. The cooling air pressure internally of the seal is so selected to accommodate the pressure reversal between the exhaust gas pressure variation (hot side) and centerbody cavity pressure (cold side). The seals are spring loaded in such a manner as to maintain contact at minimum internal seal pressure levels and pressure loaded to maintain intimate contact with the side walls during the entire operating range of the engine.